Dynon D3 interference

[wishboneash]

Hi 

I would like to reach out to the group and ask anyone who has a Dynon D3 portable attitude indicator to run a small experiment for me. I see interference on my COM radio whenever the D3 is turned on. Happens on a specific frequency, namely 121.6MHz which is of course a common ground frequency at many airports. It basically opens up the squelch and in some cases makes communication on 121.6MHz impossible. There is a fairly loud tone present which varies as the display changes on the D3 as it boots up through the menus. If anyone can test this, please get back to me with your results. I reported this to Dynon, they sent me a new replacement unit which has the same issue. I also used an SDR radio to scan the band and can see interference. I am sure there are other frequencies but I haven't come across them yet while in the plane. Also, checked it out on a portable ICOM radio. Same thing. Need to think of next steps. Thanks.

[Jerry 5TJ]

Does this radio interference happen when you run the D3 on its internal battery or only when you use the charger to the mini USB connector on the D3?

[carusoam]

https://www.dynonavionics.com/pocket-panel.php

For reference...

I wanted to look it up, so I shared it in case somebody else wants to see it...

Interesting that it may be emitting noise on a narrow frequency...
 

PP thoughts only...

Best regards,

-a-

[wishboneash]

Does this radio interference happen when you run the D3 on its internal battery or only when you use the charger to the mini USB connector on the D3?

Happens on both internal power and external power. Makes no difference with external antenna as well. I have a feeling it has to do with the display driver since tone is modulated by what's going on on the screen.

Sent from my LM-V405 using Tapatalk

[Jerry 5TJ]

You’ve narrowed the problem to the unit itself.   
Besides opening it up and modifying it to reduce EMI what’s left? 

[wishboneash]

1 hour ago, Jerry 5TJ said:

You’ve narrowed the problem to the unit itself.   
Besides opening it up and modifying it to reduce EMI what’s left? 

Will work with Dynon, being under warranty. Taking this to PM until it's resolved.

Edited January 24, 2020 by wishboneash

[Yetti]

Just checking but you don't have two comm radios tuned to the same or similar frequencies.   Sometimes the local oscillator from one radio will wack the other radio.   If you turn the D3 off does it go away?

[wishboneash]

10 minutes ago, Yetti said:

Just checking but you don't have two comm radios tuned to the same or similar frequencies.   Sometimes the local oscillator from one radio will wack the other radio.   If you turn the D3 off does it go away?

Yes. Clean as a whistle once the D3 is off. I wouldn't expect certified COM radios to radiate their local osc. to interfere with others . They are usually very well shielded. I tested the D3 at home with an SDR receiver as well as a handheld radio. The D3 interference breaks squelch on the portable at a distance of about 4 to 5 ft on 121.6 MHz.

[Yetti]

12 minutes ago, wishboneash said:

Yes. Clean as a whistle once the D3 is off. I wouldn't expect certified COM radios to radiate their local osc. to interfere with others . They are usually very well shielded. I tested the D3 at home with an SDR receiver as well as a handheld radio. The D3 interference breaks squelch on the portable at a distance of about 4 to 5 ft on 121.6 MHz.

Oh but they do.  Have had it happen with KX170s and KX155.

The D3 does not seem to have WiFi or bluetooth.   Do you have any accessories like external GPS or while running it off the DC charger?   Does it do it while running on battery only?

 

[wishboneash]

No difference with ext/int power or ext/int antenna. Also tested at home without other interfering sources. It's pretty cut and dry that the D3 is generating this interference. It could be a digital clock (typically harmonics that might be fall into the aviation band) that is left unshielded. If two new units displayed the same behavior it has to be a board design issue. 

[carusoam]

My Narco radios bled so much noise they wiped out my portable GPS signals on certain nav frequencies on the Narco...

I discovered this while navigating through Florida, heading to a VOR using the Nav, and avoiding special use airspace with the GPS...

We could watch the satellite strength disappear...on the status page...

Another source of odd signals was reported by Marauder regarding the JPI causing a squelch break...

Some examples of radio interference that can occur in modern Mooney aviation...

Best regards,

-a-

[wishboneash]

18 hours ago, carusoam said:

My Narco radios bled so much noise they wiped out my portable GPS signals on certain nav frequencies on the Narco...

I discovered this while navigating through Florida, heading to a VOR using the Nav, and avoiding special use airspace with the GPS...

We could watch the satellite strength disappear...on the status page...

Another source of odd signals was reported by Marauder regarding the JPI causing a squelch break...

Some examples of radio interference that can occur in modern Mooney aviation...

Best regards,

-a-

Anthony, I would expect new COM radios to be designed well enough to not leak RF since their main function is dealing with very low level RF signals and their on-board synthesizers are properly shielded. Also would expect their transmit sections be very carefully shielded and isolated from the receiver. Of course it's possible a malfunction (bad decoupling capacitors in the power supplies, other mechanical or electrical failures, broken solder joints etc.) could cause problems on older sets causing EMI. Did you figure out why your radios did this or was it just old avionics not playing well with the GPS receivers (which also deal with extremely low level signals buried in noise)? I wouldn't expect the same rigor say in the design of say engine monitors, attitude indicators etc which are really not dealing with RF frequencies or signal levels but do have a lot of digital circuitry and clocks that could radiate harmonics especially if the designer weren't pay attention. 

[carusoam]

Sriram,

I think you hit on it...

The Narco was designed and built in a different era...

Not only was it analog, but it was built by a small-ish mom and pop shop with not much development going on...

From the outside, it looks like they went digital with their existing Nav/Coms... everything got a D attached to the end of the product name...

As a customer, I needed some plastic gears... mine oxidized and broke... without the gears I couldn’t tune the radio and know what station I was tuning into...

They had no customer service... they wouldn’t sell me the parts... I had to send the radio in to be repaired.  My radio was probably on the shelf when the company ultimately went out of business...

I don’t miss their method of doing business...or not doing business...

1 part crummy design...

1 part aging terribly... aided by living in an outdoor plane...

1 part in the hands of a newbie learning how to fly... 

 

I probably didn’t know what I didn’t know...

There wasn’t an MS to check in with... there wasn’t a shelf of magical used radios to peruse... or even ask... “hey... is this normal?” 

Best regards,

-a-

[Yetti]

On 1/26/2020 at 8:21 PM, wishboneash said:

Anthony, I would expect new COM radios to be designed well enough to not leak RF since their main function is dealing with very low level RF signals and their on-board synthesizers are properly shielded. Also would expect their transmit sections be very carefully shielded and isolated from the receiver. Of course it's possible a malfunction (bad decoupling capacitors in the power supplies, other mechanical or electrical failures, broken solder joints etc.) could cause problems on older sets causing EMI. Did you figure out why your radios did this or was it just old avionics not playing well with the GPS receivers (which also deal with extremely low level signals buried in noise)? I wouldn't expect the same rigor say in the design of say engine monitors, attitude indicators etc which are really not dealing with RF frequencies or signal levels but do have a lot of digital circuitry and clocks that could radiate harmonics especially if the designer weren't pay attention. 

It's not within the radio.   It's two radios in proximity to another.  harmonics.  re radiation from the antenna.   One of my friends had to move his ELT antenna to the back of the plane because it was resonating via the ELT antenna between the com radios. or harmonics.  I forget.      For the D3 have you tried wrapping it in foil?

[wishboneash]

Sure, it's possible to couple through the antenna and then it would come to harmonics of one transmitter landing right on the pass band of the other receiver. No, I haven't tried the Faraday cage thing yet. I would have to ground the foil as well while keeping the display still visible! It's an intermittent problem as well, so at the moment I am still trying to figure out when it happens. Thanks.

[thinwing]

On 1/25/2020 at 6:36 AM, wishboneash said:

No difference with ext/int power or ext/int antenna. Also tested at home without other interfering sources. It's pretty cut and dry that the D3 is generating this interference. It could be a digital clock (typically harmonics that might be fall into the aviation band) that is left unshielded. If two new units displayed the same behavior it has to be a board design issue. 

My money is on a faulty or poorly designed switching power supply somewhere on the D3 s board.

[Yetti]

8 hours ago, wishboneash said:

Sure, it's possible to couple through the antenna and then it would come to harmonics of one transmitter landing right on the pass band of the other receiver. No, I haven't tried the Faraday cage thing yet. I would have to ground the foil as well while keeping the display still visible! It's an intermittent problem as well, so at the moment I am still trying to figure out when it happens. Thanks.

I am wondering if the capacitive touch screen may be the culprit.  But the power supply makes more sense.

Edited January 29, 2020 by Yetti

[wishboneash]

I will run a few more experiments to try to narrow this down by carefully recording the whole sequence from power up until the GPS locks.

[Rikk]

I have a D3 and I think I have narrowed it down to it being the source of strange strike patterns that appear on my Insight Strikefinder about half the flight.  It might be that it happens when the charging indicator is yellow battery bar (not charging) with a red exclamation point (overheated, can’t charge).  I don’t seem to have the problem when it is a green battery bar and lightning bolt.  Didn’t have the problem with the Dynon D2.

[carusoam]

Welcome aboard Rick!

Best regards,

-a-

[LANCECASPER]

This is one of the reasons why certified panel avionics are so much more expensive. A lot more time engineering and testing to pass the certification.

[wishboneash]

16 hours ago, Rikk said:

I have a D3 and I think I have narrowed it down to it being the source of strange strike patterns that appear on my Insight Strikefinder about half the flight.  It might be that it happens when the charging indicator is yellow battery bar (not charging) with a red exclamation point (overheated, can’t charge).  I don’t seem to have the problem when it is a green battery bar and lightning bolt.  Didn’t have the problem with the Dynon D2.

Hi, would you mind tuning your panel COM radio to 121.60 and see if you pick up any interference from the D3? It usually happens around the time the splash/disclaimer screen shows up. I had forgotten about this thread, but I did repeat the test with an RF spectrum analyzer (SA) and saw a signal show up at 121.6MHz. It wasn't very strong signal but it was enough for my GTN650 to pick it up. I had taken a video of the SA screen as I turned on the D3 but unfortunately I can't seem to find it now. Will try to repeat it sometime. There were a bunch of other frequencies that popped up on the SA, but none that I have run into while I have been flying. 121.6 is ground at Livermore and it is definitely annoying when it happens. To avoid this, I turn on the D3 after I am in the run up area. Dynon hasn't been of much help in resolving this.

[Rikk]

I tried 121.6, but got no noise at any point of turning the D3 on and off.  Of course, my noise on the Strikefinder goes away a lot, but still pops up sometimes, after I’ve shut off the D3, removed it, and pulled the breaker.  I’m so confused!!

[wishboneash]

20 hours ago, Rikk said:

I tried 121.6, but got no noise at any point of turning the D3 on and off.  Of course, my noise on the Strikefinder goes away a lot, but still pops up sometimes, after I’ve shut off the D3, removed it, and pulled the breaker.  I’m so confused!!

Thanks for running the experiment. Both my handheld and the panel radios pick up the noise on 121.6MHz, not all the time but most of the times. It happened with the D2 unit as well which I returned a couple of times and finally "upgraded" to the D3 which has the same issue. I give up